TORNADO AFTERMATH: In twister's path but hunkered down in modern safe room | VIDEO

May 23, 2013 - Moore, Okla., residents Vickie and Rick Green stand inside their home's garage where they recently installed an underground storm shelter. The couple recently had the shelter, in which they waited approximately 20 minutes for Monday's tornado to pass, installed. (Naudia Jawad/The Commercial Appeal)

May 23, 2013 - Moore, Okla., residents Vickie and Rick Green stand outside their home's garage where they recently installed an underground storm shelter. The couple recently had the shelter, in which they waited approximately 20 minutes for Monday's tornado to pass, installed. (Naudia Jawad/The Commercial Appeal)

MOORE, Okla. - They heard the rumble of the approaching funnel cloud, the rat-tat-tat of debris being hurled against their garage door.

But through it all, Rick and Vickie Green were safe Monday from the fearsome tornado that mowed a deadly path through western Moore, jumped Interstate 35 and bore down on their subdivision.

Like a growing number of twister-wary Oklahomans, the Greens installed an underground shelter or safe room. As the storm approached, they headed into their garage, slid open the trap-door-like entrance on the floor, and climbed in.

"We shut it up and waited for the noise to stop," recalls Rick Green.

There are no reliable figures as to how many Oklahoma residents have installed in-home safe rooms or shelters in their yards. But new initiatives are sure to boost the number, especially in the aftermath of this week's tornado that killed 24 people in Moore.

Under a two-year-old program backed by the Oklahoma Department of Emergency Management and the Federal Emergency Management Agency, residents can apply for rebates covering 75 percent of the shelter's cost, up to $2,000. Some 500 residents were approved for the rebates following the initial round of applications early last year.

In recent years, FEMA has put $57 million into the state to help pay for 11,000 residential safe rooms and 100 shelters in schools, Gov. Mary Fallin said at a press conference Thursday.

After his city was devastated for the second time in less than 15 years, Moore Mayor Glenn Lewis raised the stakes further Wednesday by announcing a proposal to change local building codes so that safe rooms are required in new houses.

The Greens, who sustained no significant damage in Monday's twister, said they decided to build their shelter in response to concerns by friends and family, including their daughter, Angela Copeland, who lives in Memphis.

"I harassed them about that for quite some time," said Copeland, 34. "It's bad enough to live in the path of tornadoes, much less not have anywhere to go when it actually happens."

The Greens, both retired, installed their shelter only last June, opting to cover the $3,500 cost and not apply for the limited rebate funds.

Consisting of a steel shell encased in concrete, the shelter is more than 6 feet long and could accommodate as many as eight people. Slots and offsets in the roof provide ventilation.

When the Greens obtained a permit for the shelter, it was registered with city officials so authorities will know to search it following heavy storm damage.

That, along with a winch kept in the shelter, addresses one worry Rick Green has about the structure. "My major concern is, if you do get hit, and stuff piles on it, how do you get out?"

Monday's storm being their first in which to use the shelter, the Greens said they were unsure what, other than bottled water, to bring with them.

But both said they're glad they have a place to go during storms. "Today I feel a whole lot better," Vickie Green said.

Adds her husband: "We've been lucky many times living here in Moore. It's time to stop pressing that luck."